JP-2011-214536A (US 2013/0087639 A1) discloses a fuel injector that includes a stator core generating an electromagnetic force by energizing a coil, a movable core moved by the electromagnetic force, and a valve body that is moved together with the movable core and opens an injection port. An elastic force of a spring and a fuel pressure are applied to the valve body in a valve-closing direction. When an attractive force (valve-opening force) according to an energization of the coil becomes greater than a closing force corresponding to the elastic force and the fuel pressure, the valve body starts a valve-opening operation.
When the coil is energized to open the valve body, the movable core is moved to and collides with the stator core. When a colliding speed is high, the movable core may rebound from the stator core. In this case, a wave causes at a ti-q line representing a relationship between an energization time ti of the coil and an injection amount q, and a variation in the injection amount is generated. Further, a damage of the movable core or the stator core may occur.